Streaming Media Supplement sa2150 and sa2250

6
This chapter explains all the possible elements of a Media-IXT deployment. Read this chapter to understand
what proxy caches do, the different scenarios in which proxy caches are deployed, and the relevant features of
Media-IXT.
This chapter has eight sections:
• “Understanding forward proxy, reverse proxy, and transparency” below
• “Understanding hierarchy” on page 12
• “Understanding live passthrough, live splitting, and hierarchical live splitting” on page 13
• “Understanding clustering” on page 15
• “Understanding VIP failover” on page 15
• “Understanding selective caching” on page 15
• “Understanding CDS preload” on page 16
• “Understanding authentication” on page 16
• “Understanding firewalls” on page 16
Understanding forward proxy, reverse proxy, and
transparency
Forward proxy, reverse proxy, and transparency are the most basic elements of any proxy cache deployment.
Here is a framework for understanding them. Keep in mind that by web clients we mean both web browsers
and streaming media players.
• Forward proxy caching is proxy caching of whatever content is requested by a particular population of web
clients. That population is defined as the clients whose requests can be intercepted by a WCCP2 router or
layer 4 switch and redirected to the proxy cache (using transparent forward proxy caching), or clients
whose browsers are explicitly configured to use a proxy cache (using non-transparent, or explicit forward
proxy caching). Figure 2-1 below illustrates forward proxy.
• Reverse proxy caching is proxy caching of whatever client requests are directed to a particular origin
server or group of origin servers. Here, the proxy cache answers to the advertised name of the origin
server(s) in question, acting for and hiding the origin server(s). There is no need to intercept and redirect
traffic, nor do clients need to be explicitly configured to use the proxy cache–so the reverse proxy cache
does not need to be transparent or explicit. Figure 2-2, on the next page, illustrates reverse proxy. (We use
the term explicit to mean non-transparent.)
2 Media-IXT Deployment Scenarios